Multiple choice

A and B can do a work in 36 days 40 days respectively. They start together but B left after some time. A finish the work 17 more days then find the time A and B worked together.

  1. 12

  2. 17

  3. 10

  4. 15

  5. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A's 1-day work = 1/36, B's 1-day work = 1/40. Let they work together for x days, then A works alone for 17 days. Total work: x(1/36 + 1/40) + 17/36 = 1. Solving: x(19/360) = 19/36, so x = 10 days. Option C is correct. Option B (17) is the time A worked alone - a common trap.

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